This invention generally relates to an illumination system. This illumination system is especially, though not exclusively, intended for use in surgical lighting in operating rooms and ambulatory surgical suites. This invention also relates to certain components which are used in the illumination system of the invention but which may also be useful in other types of optical systems and applications.
For decades, illumination systems for operating rooms have posed major problems. To ensure the safety of patients, it is essential that an illumination system provide intense and acceptably uniform illumination over the entire surgical site, which can in some cases, be of substantial width and depth as, for example in open heart surgery. Obviously, the surgery cannot be interrupted should a bulb burn out, and thus each lighting unit needs either multiple bulbs or at least a back-up bulb which will illuminate should a primary bulb fail. Also, large area systems need at least two, and preferably three or more, lighting units to ensure that light can impinge upon the surgical site from multiple directions so that no part of the surgical site is in complete shadow even when it is necessary for operating room personnel to be positioned between the surgical site and one of the lighting units. The lighting units must also be suspended so that they can be moved and rotated in all directions to provide optimum illumination of the surgical site, the size and shape of which may change during a surgical procedure.
Lighting units containing multiple high output bulbs sufficiently powerful to produce the intense lighting needed for surgery or to meet code redundancy requirements are necessarily of substantial depth and weight. To enable such large heavy lighting units to be moved by operating room personnel without requiring undue force, it is essential in practice to provide some form of counterpoise system, and the presence of the counterpoise system further increases the size and weight of the lighting units.
Conventional surgical lighting systems have other disadvantages. The powerful lamps used, which each typically comprise a bulb and a reflector, generate large amounts of heat and infra-red radiation. The heat is dissipated into the operating room, thus increasing the load on the heating, ventilating and air conditioning (HVAC) systems thereof, and is also radiated on to operating room personnel, increasing their fatigue during lengthy procedures. Since the infra-red radiation generated follows the same path as the visible light, it is thus largely absorbed at the surgical site, within the patient""s tissues. This radiation absorption by the patient""s tissues tends to damage the tissues, especially during lengthy procedures, and generally increases the trauma to the patient resulting from the operation.
It is also essential that the illumination produced by the system conform to a standard of color to ensure that tissues, blood, blood vessels, and the like. all retain their normal appearance, since any deviation from expected colors of body parts increases the risk of a surgeon mistakenly identifying a body part and thus operating incorrectly. In practice, a surgical illumination system must produce light with a proper correlated color temperature (xe2x80x9cCCTxe2x80x9d, which is defined as the absolute temperature of a black body whose chromaticity most nearly resembles that of the light source) and a proper color rendering index (xe2x80x9cCRIxe2x80x9d, which is defined as the average color shift, under illumination by a test source, of a series of eight standard colors of intermediate saturation spread throughout the range of hues, with respect to a reference source).
The need to maintain accurate CCT and CRI values presents problems when it is necessary to control the output of surgical lighting systems. Conventionally, light intensity has been controlled by varying the energy input to each lamp. However, all types of high output lamps undergo some change in their output spectrum as their energy input is varied, thus changing the CCT and CRI of the output. In practice, this tends to result in an unsatisfactory compromise since the usable intensity range is reduced and the resultant changes in CCT and CRI, though tolerable, are greater than is strictly desirable.
Attempts have been made to avoid the aforementioned longstanding disadvantages of conventional surgical lighting systems using lamps carried within lighting heads disposed inside the operating room. In particular, inventors have realized that fiber optic technology, which permits light from a remote source to be channeled through a bundle of optical fibers to a location where the light is needed, allows the development of surgical lighting systems in which the actual light sources may be outside the operating room and the light is fed to the surgical site via optical fiber bundles. Such a fiber optic based system renders the light sources accessible to technicians should a light source fail during an operation, and eases the problem of maintaining the lighting heads aseptic, since the lighting heads no longer need to contain bulbs and reflectors of complex shape. Also, the lighting heads themselves could be made smaller and lighter, thus avoiding the need for elaborate counterpoising systems. Finally, the removal of the light sources from the operating room also removes the unwanted heat generated within the operating room by conventional lighting systems.
Most proposals for use of fiber optic based lighting systems within operating rooms relate to so-called xe2x80x9csurgical headlampsxe2x80x9d, that is to say, lighting systems which provide light adjacent a surgeon""s face for illumination of a surgical site very close to the face, as required in microsurgery, for example, eye or ear surgery. Examples of such surgical headlamp systems are described in U.S. Pat. Nos. 4,516,190; 5,355,285; 5,430,620; and 5,709,459. However, at least one fiber optic based system has been proposed to replace the main conventional lighting system of an operating room; see U.S. Pat. No. 5,497,295 (Gehly), FIG. 5 et seq. In the Gehly system, the light sources are disposed within a separate room outside the operating room. Light from these sources is led via a plurality of optic fiber bundles (one bundle for each lighting head used within the operating room) into the operating room via a central hub installed in the ceiling thereof. Beneath this central hub are mounted two substantially cylindrical rotatable members having a common vertical axis. Each of the rotatable members carries a horizontal arm which extends outwardly from the rotatable member parallel to the ceiling of the operating room. A carriage is slidably mounted on each horizontal arm so as to be movable along the length of the arm, and each carriage supports a three-segment telescopic vertical column which descends from the carriage. A shallow, dish-shaped lighthead is mounted via a flexible coupling on the bottom of each telescopic column. Each of the fiber bundles entering the operating room via the central hub is led via one of the cylindrical rotatable members on to one of the horizontal arms (each arm carries only one fiber bundle) and down the associated column and flexible coupling to the center of the associated lighthead, where the light impinges upon a substantially conical central section of the lighthead, which deflects it on to a plurality of annular diffusers which surround the conical central section.
The horizontal arm/carriage/telescopic column/flexible coupling/ light-head structure described in Gehly is of considerable complexity, size and weight, so that the arms, carriages and columns appear to require powered operation (with inevitable problems should any part of the complex mechanical structure fail to operate correctly during the course of a surgical procedure), and the whole structure is probably as intrusive in an operating room as conventional lighting heads containing bulbs. Furthermore, the fiber bundles in Gehly extend unbroken from adjacent the light sources to the lightheads, with no apparent provision for relieving stress on the bundles caused by relative movements between the various parts of the supporting structure. Thus, it would appear that the apparatus does not permit completely free rotation of the arms nor more than a limited range of motion of the lightheads, and even then, wear upon, or damage to the bundles, may be expected after repeated relative movements between the various parts of the supporting structure.
Consequently, it is a primary object of the present invention to provide an illumination system, adapted for surgical lighting, which, like the Gehly system, enables the light sources to be placed remotely from an operating room, thereby reducing the bulk of the lighting heads required within the room. However, the illumination system of the present invention enables light to be transmitted from the remote sources to the lighting heads using a simpler, less bulky structure which does not require powered operation (though such operation is not excluded), and can provide means for real time control of lighting intensity and CRI.
It is also an object of the present invention to provide an illumination system which enables light from a plurality of sources to be mixed to provide uniform lighting having a desired CCT and/or CRI.
It is also an object of the present invention to provide an illumination system which enables light from a plurality of sources to be mixed to provide uniform lighting having a desired CRI and/or CCT, and which provides for feedback to ensure compliance with CRI or other color standard requirements.
It is also an object of the present invention to provide an illumination system which includes a fully rotatable fiber joint to allow a light output device fed by a fiber bundle to be freely rotated relative to parts of a fiber bundle lying on the opposed side of the joint.
It is also an object of the present invention to provide an illumination system which has a low profile lighting head using two reflectors which together provide uniform illumination over a substantial area.
It is also an object of the invention to provide a low profile lighting head employing an off-axis distributed source operating in conjunction with at least one reflector to enhance illumination control within a predetermined three-dimensional work space.
It is also an object of the present invention to provide an illumination system in which light from a single source is distributed to multiple branches. Preferred components of the present invention for use in such a distribution system include a light pipe with an embedded mirror, and a component which distributes incoming light into a plurality of fiber bundles arranged concentrically.
It is also an object of the present invention to provide an illumination system using fiber bundles in which lighting intensity is controlled by variable apertures rather than by controlling power input to a light source.
It is also an object of the present invention to provide an illumination system using fiber bundles in which light from a high intensity source is coupled into a plastic fiber bundle in such a manner that the input end of the bundle does not attain a temperature which can damage the bundle.
It is yet another object of the invention to provide a fiber based illumination system having at least one termination to a surgical light head which allows for the connection of one or more endoscope illumination or surgical headlamp fiber optic bundles or light guides.
It is yet another object of the present invention to provide an illumination system that can be focused to provide illumination patterns of different distribution.
Other objects of the invention will in part appear hereinafter and will in part be obvious when the following detailed description is read in connection with the drawings.
In general, in one aspect, this invention provides an illumination system for illuminating an area within a room, the illumination system comprising:
at least one light source;
at least one lighting head disposed within the room and arranged to output light to the area to be illuminated;
at least one light pipe and/or fiber bundle arranged to transmit light from said at least one light source to said at least one lighting head;
means for controlling the intensity of the light output from said at least one lighting head; and
means for controlling the color rendering index of the light output from said at least one lighting head.
In another aspect of this invention the aforementioned illumination system includes an alternative termination to a surgical light head which allows for the connection of one or more endoscope illumination and/or surgical headlamp fiber optic bundles or light guides.
In another aspect, this invention provides an illumination system arranged to mix the output from two separate light sources. This illumination system comprises:
first and second light sources;
a first fiber bundle having an input end arranged to receive light emitted by the first light source;
a second fiber bundle having an input end arranged to receive light emitted by the second light source,
wherein the output ends of the fibers forming the first and second fiber bundles form a single fiber bundle arranged to transmit light from both the first and second light sources; and
an optical homogenizer having an input end arranged to receive light from said single fiber bundle and an output end which delivers a substantially uniform light output.
In this illumination system, the optical homogenizer is typically a multimode light pipe, preferably provided with a plurality of facets on its circumferential surface to further enhance uniformity of mixing.
In another aspect, this invention provides an illumination system arranged to mix the output from two separate light sources and to control at least one parameter of the mixed output. This illumination system comprises:
a first light source arranged to emit light having a first characteristic value;
a second light source arranged to emit light having a second characteristic value differing from the first characteristic value;
a light mixing means arranged to receive light emitted from the first and second light sources and to produce a light output having a third characteristic value differing from the first and second characteristic values;
a light detector arranged to receive part of the light output from the light mixing means and to determine said third characteristic value of said light output; and
intensity control means arranged to vary the intensity of the light output from at least one of the first and second light sources and thereby to vary said third characteristic value of said light output from said light mixing means, said intensity control means being controlled in response to said light detector.
In this illumination system of the invention, the first, second and third characteristic values are typically values characterizing the spectral distribution of the various light fluxes involved, in particular, may be values representative of the CCT and/or CRI of the relevant light fluxes.
In another aspect, this invention provides a rotatable fiber joint for use in an illumination system. This joint comprises:
a first member having walls defining a first passage extending therethrough;
a second member disposed adjacent the first member and having walls defining a second passage extending therethrough, one end of said second passage being disposed adjacent one end of said first passage; and
a fiber optic bundle disposed within said first and second passages, the bundle being secured relative to the second member so that the bundle cannot rotate within said second passage, but not being secured to the first member so that the bundle can rotate freely within said first passage, whereby the first and second members can rotate relative to each other.
In another aspect, this invention provides a lighting head for use in an illumination system. This lighting head comprises:
input means for introducing light into the light head;
a first reflector arranged to receive light entering the lighting head through said input means and to reflect this light;
a second reflector having a plurality of facets, the second reflector being arranged to receive light reflected from the first reflector and to reflect this light to produce a substantially uniform illumination over a target area.
Preferably, in this lighting head, the first reflector is substantially conical in at least on azimuth. Also, in a preferred form of this lighting head, the output end of the fiber optic bundle has the form of an annulus surrounding the axis of the substantially conical first reflector, so that the output end of the fiber optic bundle forms an off-axis, annularly distributed light source. In yet another preferred form, the first reflector is provided as a plurality of segments concave in both azimuths where each reflector segment is illuminated by a corresponding fiber bundle that acts as a source for its associated reflector segment.
In another aspect, this invention provides an illumination system in which a single input light flux is distributed among a plurality of output fiber bundles or light pipes. This illumination system comprises:
light input means arranged to supply a single beam of light;
at least first and second light output means each comprising a fiber optic bundle or light pipe, the first and second light output means being movable relative to one another and to the light input means; and
a light distribution means arranged to receive light from the light input means, to divert a first part of the received light into the first light output means and to divert a second part of the received light into the second light output means.
In another aspect, this invention provides a light pipe which can be used in the aforementioned light distribution means. This light pipe comprises a substantially transparent rod having an axis, and a mirror surface disposed within the rod at an angle to the axis thereof, such that when light is passed axially along the rod, part of this light will be diverted by the mirror surface at an angle to the axis so as to emerge from a side surface of the rod, while the remaining light continues axially along the rod.
In another aspect, this invention provides a fiber optic device which can be used as the aforementioned light distribution means. This fiber optic device comprises:
a first bundle of optic fibers, each of said fibers in said first bundle having an input end and an output end, the input ends of said fibers being arranged to form a first surface extending substantially normal to an axis; and
a second bundle of optic fibers, each of said fibers in said second bundle having an input end and an output end, the input ends of said fibers being arranged to form a substantially annular second surface extending parallel to but outside said first surface, and the output ends of the second bundle of fibers being formed into a compact fiber bundle directed away from said axis,
the second bundle being movable relative to the first bundle so that the second surface can rotate without restriction about said axis relative to the first bundle.
This invention also provides an illumination system the light output from which is controlled by at least one variable aperture rather than by varying the power input to a light source, thereby enabling the intensity of the light output to be varied without variation in the spectral characteristics thereof. This illumination system comprises:
a first light transmission device selected from the group consisting of light pipes and fiber optic bundles, the first light transmission device having an input end and an output end;
a second light transmission device selected from the group consisting of light pipes and fiber optic bundles, the second light transmission device having an input end and an output end, the input end of the second light transmission device being disposed adjacent the output end of the first light transmission device; and
variable aperture means disposed between the output end of the first light transmission device and the input end of the second light transmission device, the variable aperture means being variable to block a varying portion of the light leaving the output end of the first light transmission device from reaching the input end of the second light transmission device, and thereby controlling the intensity of the light leaving the output end of the second light transmission device.
Finally, this invention provides a coupling device intended for coupling light from a high intensity light source into optic fibers which can be damaged by heat. This coupling device comprises:
a window arranged to receive light from the light source, the window reflecting at least part of infra-red radiation received from the light source;
optic fibers having input ends disposed adjacent the window so as to receive light passing through the window; and
a heat dissipating means in heat conducting relationship with the input ends of the optic fibers, and thereby serving to remove from said input ends heat generated within said input ends as said input ends receive light passing through the window.
Other advantages and features will become apparent from the following description and claims.